Hot top for steel ingot molds



Patented Oct. 31, 1944 UNITED STATES PATENT OFFICE 2,361,386 HOT 120?FOR STEEL INGOT MOLDS Thomas C..Eayrs, Buffalo, N. Y. Application March6, 1942, Serial No. 433,643

7 Claims.

It is well known to those skilled in the art that hot tops ofpresent-day design for usein connection with steel ingot moldsareusually made in one piece and of fire brick or other refractorymaterials which must go through a cycle of treatment at high temperaturefor an extended period of time, occupying, as they do, considerablespace in storage, and being made from material which cannot be salvaged.Where hot tops have heretofore been made of sections, these sectionshave been separate from the assembly wire and fastened together by meansof such separate wire passed around the exterior of the hot top.

One of the principal objects of my invention has been to provide a hottop which shall be made from a plurality of sections having apermanently attached wire reinforcing mesh, portions of which arelocated preferably at or near the outer surface of the sections andconnecting the panels in hinged manner.

Another object of my invention has been to construct a hot top of suchmaterial that it can be bonded by the use of a temperature sufficientonly to mature the composition but not sufilcient to oxidize theembedded Wires.

A further object of my invention has been to make my hot top ofmaterials which shall produce an endothermic effect as a result ofcontact with the molten steel, whereby the heat of the steel contactingthe hot top will be so rapidly absorbed as to quickly solidify anymolten metal which would otherwise escape through a loose joint orcrack.

Moreover, the composition of my hot top is such that a carbon dioxidegas is generated at the surface thereof which is in contact with theheated metal which gas acts as a barrier to the flow of heat to theinterior of the wall of the hot top, thereby making it possible to userelatively thin walls and yet protect the embedded wires againstexcessive heat.

Furthermore, it has been an object to use such materials in my hot topwhich will not chemically combine by direct contact with steel; eithermolten or solidified, thereby avoiding adhesion between the hot top andthe steel.

Another object has been to use a basic material for the composition ofmy hot top which is not only readily available but which in many casesconstitutes what is ordinarily waste material, thereby greatly reducingthe cost of my hot top.

Moreover, it has been an object to provide a composition for hot topsand a method of making the hot top therefrom which shallrequire onlysuflicient heat to mature the composition a but insufficient todecompose the refractory materials employed in the composition.

Another object has been to provide a hot top formed with a plurality ofpanels secured to gether by means of flexible metallic reinforcingwires, whereby the hot top when not in use may be stored in fiatposition, the wires between sections functioning as hinges when the hottop is formed into shape and ready for use, the extreme ends -of thewires projecting beyond the adjacent end surfaces of the outer sectionswhereby the entire hot top may be fastened together by twisting suchwires.

A further object of my invention has been to make my hot top of acomposition which, after the hot top has been discarded, may be used aspart of a regular standard charge to any blast furnace, thereby makingit possible to salvage the otherwise useless hot top.

The above objects and advantages have been accomplished by the devicehereinafter described, made from my composition and in accordance withmy method.

Fig. 1 is a plan view of my hottop folded and installed within the topof a steel ingot mold;

Fig. 2 is an elevational view of a steel ingot mold, partly in section,showing my hot top fully in section and in position upon the mold;

Fig. 3 is an exterior view of my hot top with the panels lying fiat inextended manner, in which position they may be conveniently stored,handled or shipped;

Fig. 4 is an edge View of my hot top showing it in the position occupiedin Fig. 3; and,

Fig. 5 is an enlarged view of portions of two adjacent panels showingthe bevel at the joining edges and a cut-away portion at the hingedjoint therebetween.

suitable molds and preferably in the positions shown in Figs. 3 and 4, Iprepare a reinforcing wire mesh. This mesh comprises a number ofcontinuous reinforcing wires l2, l3 and it spaced apart and extendinglongitudinally across all of the panels as shown in Figs. 3 and 4 andlying,

when in position, either adjacent to the outer surface of the panels orslightly embedded below such surface.

The portions of the wires and H to which they are secured preferably bymeans of welding. By providing the saw-tooth formation, the body partsof the lateral wires IE will be .embedded somewhat within the panel soas to reinforce the panels and to securethem more firmly to the wiresl2, l3 and 14. These wires are extended beyond the extreme edge of eachend panel in ends l2a, I30. and Ma. These ends are sufficiently long sothat when the panels are folded as shown in Figs. land 2, they may betwisted together so as to hold the panels firmly in position and therebyprovide a unitary structure.

As shown in Fig. 5, the lateral edge ll of each of the panels is cutaway at an angle so as to permit the folding of the hot top. So as tofacilitate the folding of the panels and to more readily bring the edgesurfaces together, it is desirable to provide a space H] betweenadjacent panels.

On the exterior surface of each of the panels there are provided lugs 6which are so positioned as to allow only a portion of the hot top toenter the mouth of the mold. These .1ugs'.may be formed integrally withthe panels in the molding thereof, or they may be made of metal andsecured to the wires l3 and M by means of welding.

In my composition, I use preferably limestone or its equivalent as abase material because it has all of the desirable characteristics, andthereby enables me to carry out the objects hereinbefore set forth.Limestone is universally available, and large quantities of wastelimestone in the form of tailings are usually procurable at low cost atplants where commercial limestone is crushed and sized. Owing to thegeneration of carbon dioxide gas caused by contact of the molten steelwith the limestone of my hot top, it is preferable to have a smallamount of combustible material as a part of my composition, wherebyporosity of the finished hot top may be had. Furthermore, it isnecessary to have a suitable bond in my composition. I have found thatthe following materials and proportions by volume are suitable: forcarrying out my invention, it being obvious that some changes in theproportions and materials may be made without departing from the spiritof my invention:

Per cent Limestone tailings, or crushed limestone,

passing inch square mesh screen '74 Saw-dust passing through the samescreen... 10 Green bond a commercially available pulverized mixtureconsisting of 3 parts strong plastic clay, one and one-half parts ofbentonite, and one and one-half parts coke-oven foundry pitch which is acokeoven residue and which, as is well known, has little adhesion up tosubstantially 350 F. (not a petroleum derivative) 6 Foundry pitch asabove described (separately added) 10 After suitable molds have beenprepared and the wire reinforcing mesh placed in position, mycomposition is placed within the molds and about the lateral reinforcingwires. The panels are then baked to a temperature of only approximately600 F. for four hours. This temperature causes the saw-dust and foundrypitch to practically disappear, leaving the panel compositionapproximately:

Percent Limestone as CaCOa (wholly non-combustible) 94 Plastic clay andbentonite (wholly noncombustible) This baking treatment of the panelsdevelops great physical strength, which, due to the reinforcement of thepanels, enables me to use a panel which is much thinner than can be usedin any hot top of present-day design.

When my hot top is .placed in use upon an ingot mold and molten steelcomes into contact with my composition, an endothermic reaction isinstantly started CaCOa-l-heat=CaCO"+COz). This endothermic reactioncontinues at a temperature far below the solidifying temperature of thesteel ingot and any liquid steel which flows in between the panels isquickly solidified. This solidified portion cannot be remelted by themolten steel behind it without re-establishing the endothermic reactionand, therefore, the portion remains solidified. Since neither calciumoxide CaO nor carbon dioxide (CO2) combine chemically with liquid orsolid steel merely by direct contact with each other, there can be noadhesion between my hot top and the steel ingot.

From the foregoing it will be understood that my composition in thecarbonate .or raw. state is at least basic. Furthermore, it will beobvious that instead of raw limestone (CaCOc), raw dolomitic limestone(CaMgC-iOe) or raw magnesite (MgCOa) may be used. It is well known tothose skilled in the art that the last two mentioned materials areseldom if ever used by the steel industry except in their calcined ordeadburned state, i. e., CO2 burned out. Due to my method ofmanufacturing, much of the limestone remains in its raw carbonate formin which form either the limestone dolomite or magnesite will sustainthe complex smelting and fluxing reactions occurring in the operation ofa blast furnace, thereby making my hot top readily salvageable as ablast furnace charge. The almost negligible weight of steel wire in themesh theoretically acts as seed in the group of reducing reactions inthe blast furnace, when liquid metallic iron is about to startseparating from the iron ore. In other words, the presence of the steelmesh in my composition when used as a blast furnace charge stimulatesthe first throwdown.

My hot top is furthermore, suitableas a blastreverts to CaCOs, it isobvious that 94% of the mineral mass of my hot top is suitable as alimestone charge of a blast furnace.

Obviously, due to the use of limestone or its equivalent, the calciningaction, produced by contact with the hot steel, generates carbon dioxidegas (CO2) which acts as a barrier to the flow of heat through the panelsof the hot top thereby providing an insulating wall of gases whichcontinue at a temperature below the solidifying temperature of theliquid steel. The presence of this gas prevents deep calciningpenetration into the panels thereby not only protecting the embeddedwire mesh but leaving the hot top in such condition that it is suitableafter normal use as a part of a blast furnace charge.

Since the small amount of combustible material is burned out of thepanels ofmy hot top during the initial baking process at lowtemperature, suitable porosity of the material is brought about. Thisporosity not only acts as a further insulator against the passage ofheat into the panels, but also provides for rapid escape of the carbondioxide gas.

While I have described the use of limestone as a basic component of mycomposition, it is obvious that any other waste or by-product, calciumhydroxide and/or calcium carbonate, procurable as waste products in manyindustrial operations, can. be substituted therefor. Instead of thefoundry pitch it is obvious that I may use any other heat-developedbinder having similar characteristics, or any other binder which willgive to my composition the desiredphysical strength.

What I claim is: a

1. A granular hot top composition composed of crushed, screenedlimestone in major amount to effect an endothermic reaction and thegeneration of carbon dioxide gas when subjected to molten steel, acombustible saw-dust to provide connecting pores in the finished productafter initial baking to permit the escape of said gas, a green bond, andfoundry pitch in minor amount but of a suificient quantity to bind thecomposition together in a coherent mass.

2. A granular hot top composition comprising substantially 74% ofcrushed screened limestone, substantially of saw-dust, substantially 6%of green bond, and substantially 10% of foundry pitch.

3. A method of making a hot top for steel ingots, comprising thepreparation of a composition consisting in major amount of metalcarbonate which is capable of decomposition when subjected to the heatof molten steel, a granular combustible material, and a bond in minoramount containing carbonaceous material, then molding said compositioninto suitable form, and then subjecting the molded form to a temperaturesuflicient to burn out the combustible material, said temperature beinginsuificient to decompose said metal carbonate, whereby connectsequentuse of the hot top.

4. A method of making a hot top for steelingots, comprising theformation of a plurality of permanently connected and reinforced panels,each being composed in major amount of a metal carbonate which issubject to decomposition in the presence of the heat of molten steel, agranular combustible material, and a bond in minor amount includingfoundry pitch and clay, and then subjecting the panels to a temperaturesufficient to burn out the combustible material, said temperature beinginsufiicient to decompose said metal carbonate, whereby connecting poresare produced in the structure permitting the escape of carbon dioxidegas upon subsequent use of the hot top.

5. The method of making a hot top comprising the formation of .a mixtureof refractory materials composed of crushed screened limestone in majoramount, saw-dust, a green" bond, and foundry pitch in minor amount,molding said composition into suitable form, and baking the hot top at atemperature sufliciently high to burn out the saw-dust and pitch but notsufilciently high to decompose the limestone, whereby connecting poresare produced in the structure permitting the escape of carbon dioxidegas upon subsequent use of the hot top.

6. A hot top comprising a walled body formed in major amount with adecomposable metal carbonate as an essential ingredient, a suitable bondin minor amount, and a granular combustible material uniformly dispersedthroughout the composition prior to the baking processduringmanufacture, whereby upon baln'ng connecting pores are produced inthe structure permitting the escape of carbon dioxide gas uponsubsequent use of the hot top.

'7. A method of making a hot top for steel ingots, comprising thepreparation of a composition having substantially '74 parts of a metalcarbonate, a substantially 10 parts of foundry pitch bond, substantially10 parts of a combustible material, and substantially 6 parts of aplastic binder, molding said composition in desired form, and thenreducing the bond and binder content of the finished product by theapplication or a temperature suflflcient to carbonize a portion of thebond and binder, whereby the finished product will contain substantially96 parts of the carbonate and substantially 4 parts of the bond andbinder. r

THOMAS C. EAYRS.

Patent No. 2 361386.

Certificate of Correction w October 31, 1944. THQMAS O. EAYRS.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requirmg correction as follows: Page 2,first column, line 61, for the words bond :1 read b0nda; andsecondcolumn, line 19, for CaCO +heat=CaCO +00 read (CaCO +heat=-Ca0+C0 andthat the said Letters Petent'should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 23rd day of January, A. 1945.

[SEAL] LESLIE FRAZER,

Acting Commissioner of Patents.

